Injury and sepsis are commonly associated with weight loss, hypermetabolism, increased nitrogen excretion and abnormal carbohydrate metabolism. New procedures and techniques are being developed which allow accurate measurements to be made in acutely ill patients without interferring with patient care. These include a special system for prolonged measurement of O2 consumption, CO2 excretion, and 14CO2 excretion --all performed without the difficulties and artifacts of a mask or mouthpiece. New techniques are being tested for the measurement of gas exchange with high inspired oxygen. Indirect calorimetry from frequent measurement of gas exchange allows the prolonged study of acutely ill surgical patients by combining daily calorie and nitrogen balance. We are currently analyzing the relative contributions of protein, fat and water to surgical weight loss. Calorie and nitrogen balance provide background data for examining the kinetics of protein breakdown and the relative contributions of 14C-alanine and glycerol to the increases in gluconeogenesis as indicated by studies with 14C-glucose. Evidence of net gain or loss of body protein will be sought by studies utilizing 14C-leucine. Tracer studies of fatty acid and triglyceride turnover will be used to examine fat mobilization during the negative calorie balance usually associated with acute injury and infection. Animal models will be used to correlate tracer data and regional metabolism. A percutaneous muscle biopsy technique is being used to measure intracellular amino acids, glycolytic intermediates and energy-rich phosphates. These procedures will be used to assay various forms of calorie and nitrogen intake toward the development of more selective guidelines for acute nutritional therapy.